TiZrCr refractory medium-entropy alloy spherical powder and preparation method and application thereof

Abstract

The invention relates to the technical field of additive manufacturing, in particular to TiZrCr refractory medium-entropy alloy spherical powder and a preparation method and application thereof. The invention provides a preparation method of TiZrCr refractory medium-entropy alloy spherical powder, which comprises the following steps: mixing Ti, Zr and Cr, and sequentially carrying out smelting, casting and hot pressing treatment to obtain an alloy electrode bar; and the alloy electrode bar serves as a consumable electrode, plasma rotating electrode atomization treatment is conducted on the alloy electrode bar, screening is conducted, and the TiZrCr refractory medium-entropy alloy spherical powder is obtained. The particle size of the TiZrCr refractory medium-entropy alloy spherical powder is smaller than 200 microns. According to the preparation method, the TiZrCr refractory medium-entropy alloy spherical powder which is high in sphericity degree, almost free of hollow powder and satellite powder and low in impurity content can be prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a TiZrCr refractory medium-entropy alloy spherical powder, a preparation method thereof, and applications thereof. Background Art

[0002] The requirements for powder quality of additive manufacturing process characteristics include but are not limited to high sphericity, good fluidity, low hollow ratio, small proportion of satellite powder and low impurity content. TiZrCr alloy is a refractory medium entropy alloy composed of three elements Ti, Zr and Cr in equal or nearly equal atomic ratios. It combines the machinability of traditional alloys with the structural stability of refractory medium entropy alloys, and shows important application potential in aerospace, deep-sea energy equipment, high-end nuclear industry and national defense and military industries. Using spherical TiZrCr alloy powder as raw material, components or coatings prepared by additive processes such as selective laser melting (SLM) and laser metal deposition (LMD) can significantly improve the comprehensive mechanical properties, high-temperature oxidation resistance and corrosion resistance of the products, meeting the use requirements of long life and reliability of key equipment in extreme service environments.

[0003] However, there are currently no reports on the preparation of spherical powder particles of TiZrCr ternary refractory medium-entropy alloys or high-concentration TiZrCr-based alloys with complex compositions, particularly high-sphericity, high-quality powders for additive manufacturing. Among existing metal powder preparation technologies, only gas atomization and plasma rotating electrode atomization can directly produce spherical powders. Previously, spherical powders of Ti, TiZr, and ZrCr-based alloys were typically prepared by vacuum melting followed by gas atomization. However, these powders generally suffer from defects such as insufficient sphericity, high surface roughness, high internal porosity, and satellite powder adhesion. Furthermore, due to their high melting points and high chemical activity, Ti and Zr are highly susceptible to high-temperature oxidation and contamination from the melting crucible, affecting purity. These defects can lead to technical issues such as impaired powder feeding flowability, weak interlayer bonding, and increased internal defects (such as pores and microcracks) in the additive manufacturing process, further compromising the dimensional accuracy, mechanical properties, and service reliability of the final product. The plasma rotating electrode atomization powder production method uses an electric arc to melt the tip of a high-speed rotating electrode rod, relying on centrifugal force to throw out molten droplets, which then solidify into powder in an inert atmosphere. The powder produced by this method has the advantages of high sphericity, less hollow powder and satellite powder, low oxygen content, and few inclusions. Therefore, it is very suitable for preparing high-purity and high-sphericity metal powders for additive manufacturing. In particular, for alloys with high chemical activity and sensitive components such as high concentrations of Ti and Zr, the advantages in improving powder quality and avoiding oxidation are more significant. However, the production of spherical powder by the rotating electrode atomization method requires processing the alloy ingot into rods suitable for high-speed rotation, with uniform composition and without casting defects. The TiZrCr three-principal refractory medium-entropy alloy has high melting points and obvious differences, high solidification shrinkage, wide solidification range, and high surface tension and viscosity, resulting in a large number of voids and looseness in its casting structure; due to the large atomic size difference and electronegativity of Cr-Zr and Cr-Ti atomic pairs, like other refractory high-entropy or medium-entropy alloys, it is easy to form a large number of non-solid solution metallic compound phases, the alloy brittleness increases sharply, and it is very easy to cause the internal casting defects of the electrode rod during the rotating electrode atomization process to become crack sources, and then initiate cracks and cause local fragmentation of the electrode rod. These factors seriously affect the powder making efficiency and powder recovery rate.

[0004] Therefore, it is very necessary to develop a method for preparing high-quality spherical powder of refractory medium-entropy alloy containing high concentrations of Ti, Zr, and Cr elements, which is of great significance for its engineering application in the field of additive manufacturing and the industrial production of high-activity new alloy spherical powder particles. Summary of the Invention

[0005] In view of this, the present invention aims to provide a TiZrCr refractory medium-entropy alloy spherical powder, a preparation method thereof, and an application thereof. The preparation method can produce a TiZrCr refractory medium-entropy alloy spherical powder with high sphericity, almost no hollow powder and satellite powder, and low impurity content.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing TiZrCr refractory medium entropy alloy spherical powder, comprising the following steps:

[0008] Ti, Zr and Cr are mixed, and smelted, cast and hot pressed in sequence to obtain an alloy electrode rod;

[0009] Using the alloy electrode rod as a consumable electrode, performing plasma rotating electrode atomization treatment on the alloy electrode rod, and sieving to obtain the TiZrCr refractory medium entropy alloy spherical powder;

[0010] The particle size of the TiZrCr refractory medium entropy alloy spherical powder is less than 200 μm.

[0011] Preferably, the purity of Ti, Zr and Cr are all ≥99.9%;

[0012] The particle sizes of Ti, Zr and Cr are independently 1 to 10 mm.

[0013] Preferably, the atomic ratio of Ti, Zr and Cr is (20-45):(20-45):(20-45).

[0014] Preferably, the smelting is carried out under vacuum conditions;

[0015] The heating power of the smelting is 160-180 kW, and the holding time of the smelting is 5-20 minutes.

[0016] Preferably, the hot pressing treatment is carried out under vacuum conditions;

[0017] The temperature of the hot pressing treatment is 900-1100° C., the pressure is 20-50 MPa, and the time is 1-3 hours.

[0018] Preferably, after obtaining the alloy electrode rod, the method further comprises fine-machining the alloy electrode rod to obtain an alloy electrode rod with a thread at one end;

[0019] The diameter of the non-threaded region of the alloy electrode rod with a thread at one end is 30-40 mm, the length is 130-180 mm, and the surface roughness is less than 0.2 mm.

[0020] Preferably, the plasma rotating electrode atomization treatment is carried out in a protective atmosphere;

[0021] The protective atmosphere is an argon atmosphere and / or a helium atmosphere; the gas pressure of the protective atmosphere is 0.04-0.09 MPa.

[0022] Preferably, the condition parameters of the plasma rotating electrode atomization treatment include: the distance between the plasma gun and the alloy electrode rod is 30 to 50 mm, the arc starting current of the plasma gun is 500 to 900 A, the arc continuing current of the plasma gun is 500 to 800 A, the rotation speed of the alloy electrode rod is 20,000 to 35,000 r / min, and the feed rate of the alloy electrode rod is 1.7 to 2.6 mm / s.

[0023] The present invention also provides TiZrCr refractory medium entropy alloy spherical powder prepared by the preparation method described in the above technical solution, which includes, by mass percentage, TiZrCr refractory medium entropy alloy spherical powder with a particle size of <75 μm, TiZrCr refractory medium entropy alloy spherical powder with a particle size of 75-150 μm, and TiZrCr refractory medium entropy alloy spherical powder with a particle size of 150-200 μm;

[0024] The mass ratio of the TiZrCr refractory medium entropy alloy spherical powder with a particle size of less than 75 μm, the TiZrCr refractory medium entropy alloy spherical powder with a particle size of 75-150 μm, and the TiZrCr refractory medium entropy alloy spherical powder with a particle size of 150-200 μm is (2-25): (30-50): (2-10);

[0025] The sphericity of the spherical alloy powder with a particle size of less than 200 μm in the TiZrCr refractory medium entropy alloy spherical powder is ≥98%, and the powder recovery rate of the spherical alloy powder with a particle size of less than 150 μm is 35% to 70%.

[0026] The present invention also provides the use of the TiZrCr refractory medium entropy alloy spherical powder described in the above technical solution as a raw material for additive manufacturing in aerospace or high-end equipment.

[0027] The present invention provides a preparation method of TiZrCr refractory medium-entropy alloy spherical powder, comprising the following steps: mixing Ti, Zr and Cr, and sequentially performing smelting, casting and hot pressing treatments to obtain an alloy electrode rod; using the alloy electrode rod as a consumable electrode, performing plasma rotating electrode atomization treatment on the alloy electrode rod, and screening to obtain the TiZrCr refractory medium-entropy alloy spherical powder; the particle size of the TiZrCr refractory medium-entropy alloy spherical powder is less than 200 μm. Compared with the powder containing high concentration of highly active elements such as Ti and Zr prepared by the existing gas atomization method, the preparation method of the present invention has higher powder particle quality, specifically high sphericity, smooth surface, almost no hollow powder and satellite powder, and very few inclusions, and uniform microstructure, excellent performance, and is suitable for high-end applications of additive manufacturing with high requirements on powder quality and performance; the TiZrCr refractory medium entropy alloy spherical powder prepared by the preparation method of the present invention through plasma rotating electrode atomization treatment has high sphericity, smooth surface, almost no hollow powder and satellite powder, and very few inclusions, and uniform microstructure, and excellent performance Excellent; by performing hot pressing treatment, the interfaces of large-scale pores and loose casting defects can be fully welded, significantly improving the density of the cast electrode rod material, while avoiding the TiZrCr alloy with a large amount of intermetallic compound brittle phase to produce obvious shape changes and microcracks during the hot pressing process, thereby avoiding the electrode rod material from stress concentration and breaking and being thrown out during the high-speed rotation of the plasma rotating electrode atomization, so that the atomization powder making process can be carried out smoothly, and the obtained spherical powder has a high powder collection rate and qualified rate, solving the technical difficulties of domestic production of TiZrCr refractory medium entropy alloy spherical powder containing high concentrations of highly active elements such as Ti and Zr. At the same time, the preparation method has a short process, low requirements for preparation equipment, convenient and easy operation, is suitable for large-scale industrial production, and has good promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a physical picture of the defects in the longitudinal section of the hot-pressed alloy bar described in Example 1;

[0029] Figure 2 The surface scanning electron micrographs of the spherical alloy powder described in Example 1 at different magnifications are shown;

[0030] Figure 3 The internal metallographic images of the spherical alloy powder described in Example 1 at different magnifications;

[0031] Figure 4 This is a scanning electron micrograph of the interior of the spherical alloy powder described in Example 1;

[0032] Figure 5 is the X-ray diffraction pattern of the spherical alloy powder described in Example 1;

[0033] Figure 6 is the nanoindentation hardness of the spherical alloy powder described in Example 1;

[0034] Figure 7 This is a physical picture of the defects in the longitudinal section of the alloy bar prepared in Comparative Example 1;

[0035] Figure 8 This is a photo of the pre-prepared alloy bar after fine processing in comparative example 1, after being exploded and thrown out during the plasma rotating electrode atomization process. DETAILED DESCRIPTION

[0036] The present invention provides a method for preparing TiZrCr refractory medium entropy alloy spherical powder, comprising the following steps:

[0037] Ti, Zr and Cr are mixed, and smelted, cast and hot pressed in sequence to obtain an alloy electrode rod;

[0038] Using the alloy electrode rod as a consumable electrode, performing plasma rotating electrode atomization treatment on the alloy electrode rod, and sieving to obtain the TiZrCr refractory medium entropy alloy spherical powder;

[0039] The particle size of the TiZrCr refractory medium entropy alloy spherical powder is less than 200 μm.

[0040] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0041] The present invention mixes Ti, Zr and Cr, and sequentially performs smelting, casting and hot pressing to obtain an alloy electrode rod.

[0042] In the present invention, the purity of the Ti, Zr and Cr is preferably ≥99.9%; the particle size of the Ti, Zr and Cr is preferably independently 1 to 10 mm.

[0043] Before the mixing, the present invention further preferably includes cleaning the Ti, Zr, and Cr. In the present invention, the cleaning is preferably performed by ultrasonic cleaning in anhydrous ethanol. The present invention does not have any particular restrictions on the frequency and time of the ultrasonic cleaning, and can be performed using a frequency and time well known to those skilled in the art.

[0044] In the present invention, the atomic ratio of Ti, Zr and Cr is preferably (20-45): (20-45): (20-45). In an embodiment of the present invention, the atomic ratio of Ti, Zr and Cr can be 34:33:33, 40:40:20 or 25:45:30.

[0045] In the present invention, the mixing is preferably carried out by placing the Ti, Zr and Cr into a water-cooled copper crucible in the order of melting points from low to high.

[0046] In the present invention, the smelting method is preferably vacuum induction levitation smelting. In the present invention, the smelting is preferably carried out under vacuum conditions, and the heating power of the smelting is preferably 160-180 kW, more preferably 160 kW, 162 kW, 164 kW, 166 kW, 168 kW, 170 kW, 172 kW, 174 kW, 176 kW, 178 kW or 180 kW; the holding time of the smelting is preferably 5-20 minutes, more preferably 5 minutes, 8 minutes, 10 minutes, 13 minutes, 16 minutes, 18 minutes or 20 minutes. In an embodiment of the present invention, the heating power of the smelting can be 160 kW, 170 kW or 165 kW, and the holding time can be 15 minutes, 10 minutes or 12 minutes.

[0047] In the present invention, the smelting process preferably includes: placing a water-cooled crucible containing Ti, Zr and Cr in a vacuum induction levitation melting furnace, first evacuating the crucible to a vacuum temperature of (1.0-9.0)×10 -3 Pa, and then introduce high-purity argon gas to 0.02-0.08MPa, repeat the vacuum and argon process more than three times to reduce the oxygen content in the furnace chamber, and then carry out smelting, and repeat the smelting for more than 3 times, in which vacuum is re-evacuated and argon is introduced after each smelting.

[0048] The present invention has no special limitation on the casting process. The casting process can be performed in a cylindrical graphite mold with an inner diameter of 30 to 40 mm using a process well known to those skilled in the art.

[0049] In the present invention, the hot pressing process preferably comprises placing the cast alloy rod into a cylindrical graphite mold with an inner diameter of 30 to 40 mm, and then placing the cast alloy rod into a vacuum hot pressing furnace for hot pressing. In the present invention, the diameter of the alloy rod is preferably less than 0.5 mm than the inner diameter of the cylindrical graphite mold.

[0050] In the present invention, the temperature of the hot pressing treatment is preferably 20 to 100°C lower than the melting point of the alloy rod. In the present invention, the temperature of the hot pressing treatment is preferably 900 to 1100°C, more preferably 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C, 1020°C, 1040°C, 1060°C, 1080°C or 1100°C; the pressure of the hot pressing treatment is preferably 20 to 50 MPa, more preferably 20 MPa, 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa or 50 MPa; the time of the hot pressing treatment is preferably 1 to 3 hours, more preferably 1 hour, 1.5 hours, 2.0 hours, 2.5 hours or 3 hours. In an embodiment of the present invention, the temperature of the hot pressing treatment may be 1050°C, 1000°C or 980°C, the pressure may be 20MPa, 25MPa or 30MPa, and the time may be 1h, 1.5h or 2h. In the present invention, the hot pressing treatment is preferably carried out under vacuum conditions, and the vacuum degree of the hot pressing treatment is preferably (1.0-9.0)×10 -3 In the embodiment of the present invention, the vacuum degree of the hot pressing process can be 6.0×10 -3 Pa, 4.0×10 -3 Pa or 3.0×10 -3 Pa.

[0051] After obtaining the alloy electrode rod, the present invention uses the alloy electrode rod as a consumable electrode and performs plasma rotating electrode atomization treatment on the alloy electrode rod to obtain the TiZrCr refractory medium entropy alloy spherical powder.

[0052] After obtaining the alloy electrode rod, the present invention preferably further includes fine-machining the alloy electrode rod to obtain an alloy electrode rod with a threaded end. The present invention does not impose any particular restrictions on the fine-machining process; it can be performed using a process well known to those skilled in the art. In the present invention, the alloy electrode rod with a threaded end preferably has a diameter of 30 to 40 mm, a length of 130 to 180 mm, and a surface roughness of less than 0.2 mm.

[0053] In the present invention, the process of the plasma rotating electrode atomization treatment is preferably to connect and fix the threaded end of the alloy rod with a thread at one end to the main shaft of the plasma rotating electrode atomization equipment, evacuate the atomization chamber, and then introduce protective gas, repeat the process of evacuating and passing protective gas for more than 3 times to reduce the oxygen content in the furnace chamber, and finally wait for the air pressure in the atomization chamber to reach the set value after the protective gas is passed, start the rotating electrode to make the alloy rod rotate at high speed, start the plasma gun to form an arc to melt the front end of the alloy rod, so that the molten droplets at the front end of the alloy rod are atomized and thrown out under the action of centrifugal force, and cool to form powder. After the powdering is completed, the air pressure in the atomization chamber is maintained for 20 to 40 minutes, and the powder is taken out after cooling.

[0054] In the present invention, the protective atmosphere is preferably an argon atmosphere and / or a helium atmosphere. When the protective atmosphere is an argon atmosphere and a helium atmosphere, the present invention does not have any particular limitation on the ratio of the argon atmosphere and the helium atmosphere, and they can be mixed in any ratio. In an embodiment of the present invention, the protective atmosphere can be an argon atmosphere.

[0055] In the present invention, the vacuum degree after vacuuming is preferably (1.0-9.0)×10 -3 In the embodiment of the present invention, the vacuum degree after evacuation can be 5.0×10 -3 Pa or 6.0×10 -3 In the present invention, the gas pressure after the shielding gas is introduced is preferably 0.04 to 0.09 MPa. In an embodiment of the present invention, the gas pressure after the shielding gas is introduced can be 0.05 MPa, 0.06 MPa or 0.09 MPa.

[0056] In the present invention, the oxygen content in the protective atmosphere is preferably ≤100 ppm.

[0057] In the present invention, the condition parameters of the plasma rotating electrode atomization treatment include: the distance between the plasma gun and the alloy electrode rod is preferably 30-50 mm, more preferably 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm, 48 mm or 50 mm; the plasma gun arc starting current is preferably 500-900 A, more preferably 500 A, 550 A, 600 A, 650 A, 700 A, 750 A, 800 A, 850 A or 900 A; the plasma gun arc continuing current is preferably 500-800 A, more preferably 500 A, 550 A, 600 A, 650 A, 700 A, 750 A or 800 A; The rotation speed of the alloy electrode rod is preferably 20,000 to 35,000 r / min, more preferably 20,000 r / min, 22,000 r / min, 24,000 r / min, 26,000 r / min, 28,000 r / min, 30,000 r / min, 32,000 r / min, 34,000 r / min or 35,000 r / min; the feed rate of the alloy electrode rod is preferably 1.7 to 2.6 mm / s, more preferably 1.7 mm / s, 1.8 mm / s, 1.9 mm / s, 2.0 mm / s, 2.1 mm / s, 2.2 mm / s, 2.3 mm / s, 2.4 mm / s, 2.5 mm / s or 2.6 mm / s. In an embodiment of the present invention, the distance between the plasma gun and the electrode rod can be 30 mm, 35 mm or 45 mm; the arc starting current of the plasma gun can be 500 A, 550 A, 800 A or 600 A; the arc continuing current of the plasma gun can be 500 A, 550 A, 800 A or 650 A; the rotation speed of the electrode rod can be 30000 r / min, 23000 r / min, 32000 r / min or 29000 r / min; the feed rate of the electrode rod can be 1.9 mm / s, 2.2 mm / s or 2.5 mm / s.

[0058] In the present invention, controlling the condition parameters of the plasma rotating electrode atomization treatment within the above-mentioned range can further control the particle size distribution and quality of the alloy powder. The fine powder of the alloy powder (particle size range is below 150 μm) has a high powder collection rate and a high spherical powder qualification rate, thereby improving production efficiency.

[0059] In the present invention, the screening is preferably performed by screen grading. The present invention does not have any special limitation on the screening process, and the screening process may be performed by a process well known to those skilled in the art.

[0060] After the screening is completed, the present invention preferably further includes collecting and vacuum packaging. The present invention does not have any special limitation on the collection and vacuum packaging process, and the process can be carried out using a process well known to those skilled in the art.

[0061] The present invention also provides TiZrCr refractory medium entropy alloy spherical powder prepared by the preparation method described in the above technical solution, which includes, by mass percentage, TiZrCr refractory medium entropy alloy spherical powder with a particle size of <75 μm, TiZrCr refractory medium entropy alloy spherical powder with a particle size of 75-150 μm, and TiZrCr refractory medium entropy alloy spherical powder with a particle size of 150-200 μm;

[0062] The mass ratio of the TiZrCr refractory medium entropy alloy spherical powder with a particle size of less than 75 μm, the TiZrCr refractory medium entropy alloy spherical powder with a particle size of 75-150 μm, and the TiZrCr refractory medium entropy alloy spherical powder with a particle size of 150-200 μm is (2-25): (30-50): (2-10);

[0063] The sphericity of the spherical alloy powder with a particle size of less than 200 μm in the TiZrCr refractory medium entropy alloy spherical powder is ≥98%, and the powder recovery rate of the spherical alloy powder with a particle size of less than 150 μm is 35% to 70%.

[0064] The present invention also provides the use of the TiZrCr refractory medium entropy alloy spherical powder described in the above technical solution in additive manufacturing. The present invention does not have any particular limitations on the method of the application, and the method can be performed using methods well known to those skilled in the art.

[0065] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0066] Example 1

[0067] Ti 34 Zr 33 Cr 33 Preparation method of refractory medium entropy alloy spherical powder:

[0068] Titanium with a purity of ≥99.9% and a particle size of 1 to 10 mm, zirconium with a purity of ≥99.9% and a particle size of 1 to 10 mm, and chromium with a purity of ≥99.9% and a particle size of 1 to 10 mm are placed in anhydrous ethanol and ultrasonically vibrated to remove surface oil and impurities, thereby obtaining pretreated titanium, pretreated zirconium, and pretreated chromium, respectively.

[0069] According to the atomic ratio of 34:33:33, pretreated titanium, pretreated zirconium and pretreated chromium (in order of melting point from low to high) were placed in a water-cooled copper crucible in a vacuum induction levitation melting furnace. The pressure in the furnace was first reduced to 5.0×10 -3 Pa, then introduce high-purity argon to 0.04MPa, repeat the vacuum and argon process three times to reduce the oxygen content in the furnace chamber, increase the power to 160kW for smelting, keep warm for 15min, and repeat the smelting at least three times, wherein vacuum is re-evacuated and argon is introduced after each smelting. After the master alloy is fully smelted to ensure uniform composition, the alloy melt from the last smelting is cast into a cylindrical graphite mold with an inner diameter of 34mm to obtain a pre-prepared alloy bar;

[0070] The pre-prepared alloy rod was placed in a cylindrical graphite mold with an inner diameter of 34.5 mm in a vacuum hot pressing sintering furnace for hot pressing treatment: first, vacuum was drawn to 3.0×10 -3 Pa, then heated to 1050 ° C (heating rate of 10 ° C / min), maintained at 20 MPa for 1 h, and cooled to obtain hot-pressed alloy bars;

[0071] The hot pressed alloy rod was finely processed to obtain an alloy electrode rod with a thread at one end (diameter 34 mm, length 140 mm, surface roughness <0.2 mm);

[0072] The alloy electrode rod with thread at one end is used as a consumable electrode, and its threaded end is connected and fixed to the main shaft of the plasma rotating electrode atomization equipment, and the atomization chamber is evacuated to 5.0×10 -3 After the furnace reaches 500 MPa, high-purity argon gas is introduced to maintain the gas pressure at 0.05 MPa. The vacuum pumping and argon gasification process is repeated at least three times to reduce the oxygen content in the furnace chamber. Subsequently, the rotating electrode and plasma gun are started to atomize and pulverize the electrode rod (the distance between the plasma gun and the electrode rod is 30 mm, the arc starting current of the plasma gun is 500 A, the continuous arc current of the plasma gun is 500 A, the electrode rod rotation speed is 30,000 r / min, and the electrode rod feeding rate is 1.9 mm / s) to obtain spherical alloy powder;

[0073] The spherical alloy powder was placed in a sieve filled with argon gas by a screening and grading method, and was screened and collected to obtain spherical alloy powder with a particle size of less than 75 μm, spherical alloy powder with a particle size of 75 to 150 μm, spherical alloy powder with a particle size of 150 to 200 μm, and spherical alloy powder with a particle size greater than or equal to 200 μm (the distribution of spherical alloy powders in the above particle size ranges is shown in Table 1), and each was vacuum packaged.

[0074] Cut along the longitudinal section of the hot pressed alloy bar to observe the defects in the core area of the entire hot pressed alloy bar. Figure 1 This is a physical picture of the defects in the longitudinal section of the hot pressed alloy bar. Figure 1 It can be seen that the casting defects such as pores and conveying inside the hot pressed alloy bar have been eliminated and the bar is completely dense.

[0075] The sphericity of the spherical alloy powder was tested according to the standard of GB / T14992, and the hollow rate of the spherical alloy powder was tested according to the standard of GB / T41978. The sphericity of the spherical alloy powder with a particle size of less than 200 μm was greater than 98%, and the powder recovery rate of the spherical alloy powder with a particle size of less than 150 μm was 67.1%, with almost no hollow powder.

[0076] Figure 2 The surface scanning electron microscope images of the spherical alloy powder with a particle size of less than 150 μm at different magnifications are shown. Figure 3 The internal metallographic images of the spherical alloy powder with a particle size of less than 150 μm at different magnifications are shown in FIG. Figures 2-3 It can be seen that the spherical alloy powder of the present invention has high sphericity, smooth surface, and almost no hollow powder and satellite powder;

[0077] Figure 4 is a scanning electron microscope image of the interior of the spherical alloy powder with a particle size of less than 150 μm, Figure 5 is the X-ray diffraction pattern of the spherical alloy powder with a particle size of less than 150 μm, Figures 4-5 It can be seen that the internal structure of the spherical alloy powder consists of a BCC matrix phase and a Cr2(Ti, Zr) intermetallic compound phase, and the composition is uniform;

[0078] Figure 6 is the nanoindentation hardness of the spherical alloy powder with a particle size of less than 150 μm, Figure 6 It can be seen that the nanoindentation hardness of the spherical alloy powder is 4.52 GPa, indicating that the spherical alloy powder has excellent mechanical properties.

[0079] Example 2

[0080] Ti 34 Zr 33 Cr 33 The preparation method of refractory medium entropy alloy spherical powder is based on Example 1, except that when the plasma rotating electrode atomization powder is produced in the plasma rotating electrode atomization device, the rotation speed of the electrode rod is 27000 r / min; spherical alloy powder is obtained (the sphericity of the spherical alloy powder with a particle size of less than 200 μm is greater than 98%, and the powder recovery rate of the spherical alloy powder with a particle size of less than 150 μm is 58.5%).

[0081] The spherical alloy powder was placed in a sieve filled with argon gas by a screening and grading method, and was screened and collected to obtain spherical alloy powder less than 75 μm, spherical alloy powder of 75 to 150 μm, spherical alloy powder of 150 to 200 μm, and spherical alloy powder greater than or equal to 200 μm (the distribution of spherical alloy powders in the above particle size ranges is shown in Table 1), and vacuum packaged respectively.

[0082] Example 3

[0083] Ti 34 Zr 33 Cr 33 The preparation method of the refractory medium entropy alloy spherical powder is based on Example 1, except that when the plasma rotating electrode atomization powder is produced in the plasma rotating electrode atomization equipment, the plasma gun arc starting current is 550A, the plasma gun arc continuing current is 550A, and the click rod speed is 23000r / min; spherical alloy powder is obtained (the sphericity of the spherical alloy powder below 200μm is above 98%, and the powder recovery rate of the spherical alloy powder with a particle size of less than 150μm is 44.1%).

[0084] The spherical alloy powder was placed in a sieve filled with argon gas by a screening and grading method, and was screened and collected to obtain spherical alloy powder less than 75 μm, spherical alloy powder of 75 to 150 μm, spherical alloy powder of 150 to 200 μm, and spherical alloy powder greater than or equal to 200 μm (the distribution of spherical alloy powders in the above particle size ranges is shown in Table 1), and vacuum packaged respectively.

[0085] Example 4

[0086] Ti 34 Zr 33 Cr 33 The preparation method of the refractory medium entropy alloy spherical powder is based on Example 1, except that when the plasma rotating electrode atomization powder is prepared in the plasma rotating electrode atomization equipment, the plasma gun arc starting current is 800A, the plasma gun arc continuing current is 800A, and the click rod speed is 23000r / min; spherical alloy powder is obtained (the sphericity of the spherical alloy powder below 200μm is above 98%, and the powder recovery rate of the spherical alloy powder with a particle size of less than 150μm is 39.7%).

[0087] The spherical alloy powder was placed in a sieve filled with argon gas by a screening and grading method, and was screened and collected to obtain spherical alloy powder less than 75 μm, spherical alloy powder of 75 to 150 μm, spherical alloy powder of 150 to 200 μm, and spherical alloy powder greater than or equal to 200 μm (the distribution of spherical alloy powders in the above-mentioned particle size ranges is shown in Table 1, among which spherical alloy powder products greater than or equal to 200 μm were unqualified and were removed after screening), and were vacuum packaged respectively.

[0088] Table 1 Particle size distribution of the spherical alloy powders described in Examples 1 to 4 (%)

[0089] Example Example 1 Example 2 Example 3 Example 4 <75μm 21.0 18.6 8.5 5.1 75~150μm 46.1 39.9 35.6 34.6 150~200μm 4.6 3.3 8.5 8.3 ≥200μm 28.3 38.2 47.4 52.0

[0090] As shown in Table 1, the Ti 34 Zr 33 Cr 33 The particle size improvement effect of the refractory medium entropy alloy spherical powder is very obvious, indicating that the preparation method of the TiZrCr refractory medium entropy alloy spherical powder provided by the present invention can not only improve the quality of the TiZrCr refractory medium entropy alloy spherical powder, but also effectively reduce the particle size of the TiZrCr refractory medium entropy alloy spherical powder, increase the fine powder collection rate, and thus improve the overall economic efficiency. Most of the alloy powders with a particle size range of more than 200 μm are irregular block or flaky powders with a size greater than 500 μm. These unqualified powders are caused by local peeling of the tip of the electrode rod during the plasma rotating electrode atomization process. When the powder making current intensity is too large or the electrode rod speed is reduced, the proportion of flaky powder increases, mainly because the current is too large, which increases the melting volume of the rod per unit time, thereby changing the molten droplet atomization and fragmentation mode to a liquid film fragmentation mode, and the particle size of the obtained alloy powder becomes larger, and the fine powder collection rate and qualified rate of the spherical powder are reduced.

[0091] Example 5

[0092] Ti 40 Zr 40 Cr 20 Preparation method of refractory medium entropy alloy spherical powder:

[0093] Titanium with a purity of ≥99.9% and a particle size of 1 to 10 mm, zirconium with a purity of ≥99.9% and a particle size of 1 to 10 mm, and chromium with a purity of ≥99.9% and a particle size of 1 to 10 mm are placed in anhydrous ethanol and ultrasonically vibrated to remove surface oil and impurities, thereby obtaining pretreated titanium, pretreated zirconium, and pretreated chromium, respectively.

[0094] According to the atomic ratio of 40:40:20, pretreated titanium, pretreated zirconium and pretreated chromium (in order of melting point from low to high) were placed in a water-cooled copper crucible in a vacuum induction levitation melting furnace. The pressure in the furnace was first reduced to 7.0×10 -3 Pa, then introduce high-purity argon to 0.06MPa, repeat the vacuum and argon process three times to reduce the oxygen content in the furnace chamber, increase the power to 170kW for smelting, keep warm for 10 minutes, and repeat the smelting at least three times, wherein vacuum is re-evacuated and argon is introduced after each smelting. After the master alloy is fully smelted to ensure uniform composition, the alloy melt from the last smelting is cast into a cylindrical graphite mold with an inner diameter of 34mm to obtain a pre-prepared alloy bar;

[0095] The pre-prepared alloy rod was placed in a cylindrical graphite mold with an inner diameter of 34.5 mm inside a vacuum hot pressing sintering furnace, and vacuumed to 4.0×10 -3 Pa, then heated to 1000 ° C (heating rate of 10 ° C / min), 25 MPa pressure for 1.5 hours, cooled to obtain a hot pressed alloy bar (testing showed that the porosity and conveying defects inside the hot pressed alloy bar have been eliminated and the bar is completely dense);

[0096] The hot pressed alloy rod was finely processed to obtain an alloy electrode rod with a thread at one end (diameter 34 mm, length 150 mm, surface roughness <0.2 mm);

[0097] The alloy electrode rod with thread at one end is used as a consumable electrode, and its threaded end is connected and fixed to the main shaft of the plasma rotating electrode atomization equipment, and the atomization chamber is evacuated to 5.0×10 -3 After the furnace reaches 500 Pa, high-purity argon gas is introduced to maintain the gas pressure at 0.06 MPa. The vacuum and argon gas processes are repeated at least three times to reduce the oxygen content in the furnace chamber. Subsequently, the rotating electrode and plasma gun are started to atomize and pulverize the electrode rod (the distance between the plasma gun and the electrode rod is 35 mm, the arc starting current of the plasma gun is 600 A, the continuous arc current of the plasma gun is 500 A, the electrode rod rotation speed is 32000 r / min, and the electrode rod feeding rate is 2.2 mm / s) to obtain spherical alloy powder;

[0098] The spherical alloy powder is placed in a sieve filled with argon gas by a screening and grading method, and is screened and collected to obtain spherical alloy powder less than 75 μm, spherical alloy powder of 75 to 150 μm, spherical alloy powder of 150 to 200 μm, and spherical alloy powder greater than or equal to 200 μm. (The distribution of spherical alloy powders in the above-mentioned particle size ranges is as follows: the sphericity of spherical alloy powders with a particle size of less than 200 μm is greater than 98%, and the powder recovery rate of spherical alloy powders with a particle size of less than 150 μm is 69.4%. The spherical alloy powders have high sphericity, a smooth surface, almost no hollow powder and satellite powder, uniform internal structure and composition, and a nanoindentation hardness of the powder particles of 4.81 GPa. The powders are then vacuum packaged.

[0099] Example 6

[0100] Ti 25 Zr 45 Cr 30 Preparation method of refractory medium entropy alloy spherical powder:

[0101] Titanium with a purity of ≥99.9% and a particle size of 1 to 10 mm, zirconium with a purity of ≥99.9% and a particle size of 1 to 10 mm, and chromium with a purity of ≥99.9% and a particle size of 1 to 10 μm are placed in anhydrous ethanol and ultrasonically vibrated to remove surface oil and impurities, thereby obtaining pretreated titanium, pretreated zirconium, and pretreated chromium, respectively.

[0102] According to the atomic ratio of 25:45:30, pretreated titanium, pretreated zirconium and pretreated chromium (in order of melting point from low to high) were placed in a water-cooled copper crucible in a vacuum induction levitation melting furnace. The pressure in the furnace was first reduced to 2.0×10 -3 Pa, then introduce high-purity argon to 0.07MPa, repeat the vacuum and argon process three times to reduce the oxygen content in the furnace chamber, increase the power to 165kW for smelting, keep warm for 12 minutes, and repeat the smelting at least three times, wherein vacuum is re-evacuated and argon is introduced after each smelting. After the master alloy is fully melted to ensure uniform composition, the alloy melt from the last smelting is cast into a cylindrical graphite mold with an inner diameter of 34mm to obtain a pre-prepared alloy bar;

[0103] The pre-prepared alloy rod was placed in a cylindrical graphite mold with an inner diameter of 34.5 mm inside a vacuum hot pressing sintering furnace, and vacuumed to 6.0×10 -3 Pa, then heated to 980 ° C (heating rate of 10 ° C / min), 30 MPa pressure for 2 hours, cooled to obtain a hot pressed alloy bar (testing showed that the porosity and conveying defects inside the hot pressed alloy bar have been eliminated and the bar is completely dense);

[0104] The hot pressed alloy rod was finely processed to obtain an alloy electrode rod with a thread at one end (diameter 34 mm, length 140 mm, surface roughness <0.1 mm);

[0105] The alloy electrode rod with thread at one end is used as a consumable electrode, and its threaded end is connected and fixed to the main shaft of the plasma rotating electrode atomization equipment, and the atomization chamber is evacuated to 6.0×10 -3 After the furnace reaches 300 MPa, high-purity argon gas is introduced to maintain the gas pressure at 0.09 MPa. The vacuum pumping and argon gasification process is repeated at least three times to reduce the oxygen content in the furnace chamber. Subsequently, the rotating electrode and plasma gun are started to atomize and pulverize the electrode rod (the distance between the plasma gun and the electrode rod is 45 mm, the arc starting current of the plasma gun is 800 A, the continuous arc current of the plasma gun is 650 A, the electrode rod rotation speed is 29000 r / min, and the electrode rod feeding rate is 2.5 mm / s) to obtain spherical alloy powder;

[0106] The spherical alloy powder is placed in a sieve filled with argon gas by a screening and grading method, and is screened and collected to obtain spherical alloy powder less than 75 μm, spherical alloy powder of 75 to 150 μm, spherical alloy powder of 150 to 200 μm, and spherical alloy powder greater than or equal to 200 μm. (The distribution of spherical alloy powders in the above-mentioned particle size ranges is as follows: the sphericity of spherical alloy powders with a particle size of less than 200 μm is greater than 98%, and the powder recovery rate of spherical alloy powders with a particle size of less than 150 μm is 64.5%. The spherical alloy powders have high sphericity, a smooth surface, almost no hollow powder and satellite powder, uniform internal structure and composition, and a nanoindentation hardness of the powder particles of 4.13 GPa. The powders are then vacuum packaged.

[0107] Comparative Example 1

[0108] Referring to Example 1, the difference is that the hot pressing process is omitted, and the defects of the longitudinal section of the pre-prepared alloy bar are shown in the figure below. Figure 7 As shown by Figure 7 It can be seen that the pre-prepared alloy bar has a large number of casting defects such as pores and looseness in the core area from top to bottom;

[0109] After the obtained pre-prepared alloy rod is finely processed according to Example 1, the tip of the rod will explode and be thrown out during the plasma rotating electrode atomization process, resulting in the scrapping of the electrode rod, causing damage to the equipment and forcing the pulverizing process to be terminated (such as Figure 8 As shown, Figure 8 (This is a photo of the pre-prepared alloy bar after fine processing, which explodes and is thrown out during the plasma rotating electrode atomization process).

[0110] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing TiZrCr refractory medium entropy alloy spherical powder, characterized in that: The following steps are involved: Ti, Zr and Cr are mixed, and smelted, cast and hot pressed in sequence to obtain an alloy electrode rod; Using the alloy electrode rod as a consumable electrode, performing plasma rotating electrode atomization treatment on the alloy electrode rod, and sieving to obtain the TiZrCr refractory medium entropy alloy spherical powder; The particle size of the TiZrCr refractory medium entropy alloy spherical powder is less than 200 μm.

2. The preparation method according to claim 1, wherein The purity of Ti, Zr and Cr are all ≥99.9%; The particle sizes of Ti, Zr and Cr are independently 1 to 10 mm.

3. The preparation method according to claim 1 or 2, wherein The atomic ratio of Ti, Zr and Cr is (20-45): (20-45): (20-45).

4. The preparation method according to claim 1, wherein The smelting is carried out under vacuum conditions; The heating power of the smelting is 160-180 kW, and the holding time of the smelting is 5-20 minutes.

5. The preparation method according to claim 1, wherein The hot pressing treatment is carried out under vacuum conditions; The temperature of the hot pressing treatment is 900-1100° C., the pressure is 20-50 MPa, and the time is 1-3 hours.

6. The preparation method according to claim 1, wherein After obtaining the alloy electrode rod, the method further includes fine-processing the alloy electrode rod to obtain an alloy electrode rod with a thread at one end; The diameter of the non-threaded region of the alloy electrode rod with a thread at one end is 30-40 mm, the length is 130-180 mm, and the surface roughness is less than 0.2 mm.

7. The preparation method according to claim 1, wherein The plasma rotating electrode atomization treatment is carried out in a protective atmosphere; The protective atmosphere is an argon atmosphere and / or a helium atmosphere; the gas pressure of the protective atmosphere is 0.04-0.09 MPa.

8. The preparation method according to claim 1 or 7, wherein The condition parameters of the plasma rotating electrode atomization treatment include: the distance between the plasma gun and the alloy electrode rod is 30-50 mm, the plasma gun arc starting current is 500-900 A, the plasma gun arc continuing current is 500-800 A, the rotation speed of the alloy electrode rod is 20,000-35,000 r / min, and the feed rate of the alloy electrode rod is 1.7-2.6 mm / s.

9. The TiZrCr refractory medium entropy alloy spherical powder prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The invention comprises TiZrCr refractory medium entropy alloy spherical powder with a particle size of less than 75 μm, TiZrCr refractory medium entropy alloy spherical powder with a particle size of 75 to 150 μm, and TiZrCr refractory medium entropy alloy spherical powder with a particle size of 150 to 200 μm; The mass ratio of the TiZrCr refractory medium entropy alloy spherical powder with a particle size of less than 75 μm, the TiZrCr refractory medium entropy alloy spherical powder with a particle size of 75-150 μm, and the TiZrCr refractory medium entropy alloy spherical powder with a particle size of 150-200 μm is (2-25): (30-50): (2-10); The sphericity of the spherical alloy powder with a particle size of less than 200 μm in the TiZrCr refractory medium entropy alloy spherical powder is ≥98%, and the powder recovery rate of the spherical alloy powder with a particle size of less than 150 μm is 35% to 70%.

10. Use of the TiZrCr refractory medium entropy alloy spherical powder according to claim 9 as a raw material for additive manufacturing in aerospace or high-end equipment.

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